In fillet weld terminology, which dimension is used to describe weld size?

• A. Theoretical Throat
• B. Leg Length
• C. Effective Throat
• D. Weld Length

Answer: (B)

Fillet weld size is described by the leg length—the distance along each leg of the weld’s triangular cross-section where the plates meet. This dimension is used on drawings to specify how much material fills the joint along the sides of the weld. The theoretical throat and effective throat are derived measurements used for strength calculations, not for sizing the weld itself, while weld length refers to how long the weld runs along the joint. So, specifying the leg length tells you the cross‑section size of the fillet weld (for example, a 1/4 inch leg length means the weld cross‑section is that size, even if the weld runs for many inches along the joint).